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View papadan's profile

Need some math help

by papadan
posted 05-19-2017 04:32 AM


21 replies so far

View Rich's profile

Rich

5967 posts in 1471 days


#1 posted 05-19-2017 05:00 AM

42

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

View papadan's profile

papadan

3584 posts in 4250 days


#2 posted 05-19-2017 05:01 AM

42 for which part?

View Rich's profile

Rich

5967 posts in 1471 days


#3 posted 05-19-2017 05:15 AM

I was being a jerk, papadan. 42 is the The Answer to the Ultimate Question of Life, The Universe, and Everything, from the The Hitchhiker’s Guide to the Galaxy.

Seriously though, that’s a dodecahedron. A prism with 12 sides. The one you show is a regular dodecahedron. I did a web search for “angles to cut a regular dodecahedron” and it returned a number of results that might assist you. Sorry, that’s about all my brain can handle :)

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

View papadan's profile

papadan

3584 posts in 4250 days


#4 posted 05-19-2017 05:52 AM

Ok Rich. I followed a couple links supposed to show how to cut them but they just want to sell them.

View Woodknack's profile

Woodknack

13503 posts in 3261 days


#5 posted 05-19-2017 06:01 AM

I don’t know the answer but this might put you on the right track
http://woodgears.ca/geodesic/

-- Rick M, http://thewoodknack.blogspot.com/

View MrUnix's profile

MrUnix

8239 posts in 3080 days


#6 posted 05-19-2017 06:04 AM

Or this thread: dodecahedron

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

View Rich's profile

Rich

5967 posts in 1471 days


#7 posted 05-19-2017 06:04 AM

I feel your pain buddy. It’s a complicated compound angle, but once you nail it, you can cut them all day. I could do the math, but then I’d have to charge you for the answer :)

This looks helpful: https://www.youtube.com/watch?v=YxPVGe0PR5g

There are probably more, but a lot of them look like a solid surface solution, not a frame.

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

View AlaskaGuy's profile

AlaskaGuy

6108 posts in 3190 days


#8 posted 05-19-2017 06:40 AM

If you don’t have all the answers don’t hang that above a boat cradle. :)

I just had to.

-- Alaskan's for Global warming!

View papadan's profile

papadan

3584 posts in 4250 days


#9 posted 05-19-2017 07:11 AM

Rich, that video gave me everything I needed. Thank you to all who replied.

View mudflap4869's profile

mudflap4869

2081 posts in 2340 days


#10 posted 05-19-2017 10:02 AM

They tried to teach me how to use a slide rule. I quit school and got a GED. I finally learned enough algebra to get my degree in Creative Writing then promptly forgot all I had learned about math.

-- Still trying to master kindling making

View JCamp's profile

JCamp

1229 posts in 1432 days


#11 posted 05-19-2017 10:39 AM

I think the most interesting thing is that you were awake from midnight to 3am for this thread papadan…

-- Whatsoever thy hand findeth to do, do it with all thy might

View EricTwice's profile

EricTwice

248 posts in 1415 days


#12 posted 05-19-2017 11:08 AM

The interior angles of a pentagon are 108 degrees and they are mitered at 54 degrees.

A problem arises with the the angle of the faces to each other I believe this is called the dihedral angle and is 116.56 degrees. (check me on this) It is critical. You don’t have to miter it, you just have to have it in the exact middle at the top of your stock for your frames to line up properly. You will miter stock upside down. This way when you cut the miters right and left, the space for the third side automatically happens.

(this keeps you from having to figure out the compound miter.)

You should be able set up a jig and get all your pieces right and the same. Make lots of extra stock you will burn through it getting your angles correct.

once you have the angles solved, you will need to have some kind of joinery in the miter so they will stay together.

Looks like a fun project

-- nice recovery, They should pay extra for that mistake, Eric E.

View steliart's profile

steliart

2895 posts in 3569 days


#13 posted 05-19-2017 12:19 PM

I hope this could help a bit my friend :)

-- Stelios L.A. Stavrinides: - I am not so rich to buy cheap tools, but... necessity is the mother of inventions !!!

View dhazelton's profile

dhazelton

2839 posts in 3178 days


#14 posted 05-19-2017 12:22 PM

If it was me I’d just buy the freakin’ thing.

View EricTwice's profile

EricTwice

248 posts in 1415 days


#15 posted 05-19-2017 01:53 PM



If it was me I d just buy the freakin thing.

- dhazelton

But what’s the fun of that?

-- nice recovery, They should pay extra for that mistake, Eric E.

View shipwright's profile

shipwright

8595 posts in 3679 days


#16 posted 05-19-2017 02:19 PM

I used 31 3/4 degrees for this one. There is a blog attached.
http://lumberjocks.com/projects/43503

-- Paul M ..............the early bird may get the worm but it’s the second mouse that gets the cheese! http://thecanadianschooloffrenchmarquetry.com/

View Jim Bertelson's profile

Jim Bertelson

4275 posts in 4046 days


#17 posted 05-19-2017 03:24 PM

That is way too much to contemplate before 0800 hrs, Dan, but it looks like you got a bunch of help.

Once I was really good at math, but then like Mudflat, I forgot it all. That is a head scratcher for sure.

-- Jim, Anchorage Alaska

View papadan's profile

papadan

3584 posts in 4250 days


#18 posted 05-19-2017 08:11 PM



I think the most interesting thing is that you were awake from midnight to 3am for this thread papadan…

- JCamp


I don’t sleep much anymore! LOL

View papadan's profile

papadan

3584 posts in 4250 days


#19 posted 05-19-2017 08:17 PM



If it was me I d just buy the freakin thing.

- dhazelton


If I wanted one of these I probably would buy it. My woodworking club came up with a one board challenge and gave me a Walnut board to use. We have to even take the scrap back to show how much of the board we used and can only use 10% of any other wood and any hardware we want. I am either going to make a double hanging lamp or a single Dodehedaron table lamp with an Edison bulb. Just have to figure out how many pieces I can stretch this board into.

View papadan's profile

papadan

3584 posts in 4250 days


#20 posted 05-19-2017 08:24 PM

I want to that everyone who replied. in the 80s I taught my Son Algebra and Geometry, throughout my career I used math to design and build cranes and control systems. Radiation and Chemo have a way of destroying brain function I guess, because I have trouble with what day it is. I just write down notes on whatever I need to know now like these angles and diagrams of which way to hold the wood to cut them. LOL

View Karda's profile

Karda

2524 posts in 1435 days


#21 posted 05-19-2017 10:38 PM

I’m with ya papadan my math is almost nonexistant as well

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